Recently, instead of an optical endoscope (called also a fiber scope) wherein an optical image formed by an objective in the tip part of an insertable part is transmitted to the base end side through an image guide formed of a fiber bundle, there has been developed an electronic endoscope (which shall be called an electronic scope hereinafter) wherein an optical image formed by an objective is photoelectrically converted to an electric signal by a solid state imaging device (which shall be abbreviated as an SID hereinafter) such as a charge coupled device (which shall be abbreviated as a CCD hereinafter) and the electric signal is transmitted to the base and can be displayed through a video processor.
With the above mentioned electronic scope, not only is a light source apparatus required, as in the fiber scope, but also a signal processing means for processing signals is required.
Now, even in the above mentioned fiber scope, if a TV camera is fitted to the eyepiece part of this fiber scope, signals can be processed by the signal processing means common with the electronic endoscope. Such an apparatus is disclosed in the gazette of a Japanese patent laid open No. 243625/1985.
In the above mentioned prior art example, by using a common signal processing means, there can be made an economical apparatus wherein either of an electronic scope or a fiber scope externally fitted with a TV camera can be used.
In the above mentioned prior art example, an economical apparatus can be realized but there have been defects. Since as a common signal processing means is used, the number of pixels of the SID used in the externally fitted camera will be the same as the number of pixels of the SID and, even when a fiber scope is filled thereto even though the number of fibers forming the image guide of the fiber scope is large. Thus, the resolution cannot be improved externally fitted camera is attached.